Engine oil is used to lubricate internal combustion engine components. The oil reduces friction and wear on moving parts, such as at piston rings, pistons rods, cylinder walls, crankcase, etc. Engine oil levels may be intermittently monitored, while a vehicle is stationary, to avert premature engine degradation. In particular, oil changes are prescribed when a sensed engine oil level falls below a threshold. The desire to increase the time period between engine oil changes, as well as the natural tendency of engines to burn engine oil and/or develop minor leaks has led to an increased importance in the monitoring of engine oil levels.
One example of an engine oil level sensor is shown by Bezard et al. in U.S. Pat. No. 4,513,616. Therein, a resistive wire probe (or “hot wire”) is partially immersed in the liquid whose level is being sensed. Electrical energy is applied to the probe at different time points and a change in a measured electrical parameter of the probe is correlated with liquid level. Still other approaches include use an oil pressure sensor to infer engine oil level.
However, the inventors herein have recognized potential issues with such systems. As one example, by the time the pressure sensor infers that the oil level is below a threshold, the engine may already have experienced some level of irreversible degradation. As another example, the oil level measurement may require the vehicle to be stationary, as lateral and longitudinal acceleration experienced during vehicle motion can corrupt sensor outputs and generate false level readings. Thus if the oil level drops while the vehicle is in motion, the low oil level may not be detectable until the vehicle has come to a rest, by which time, the continued low engine oil level may have caused significant engine degradation. Furthermore, since engine oil is constantly being pumped throughout the engine, different pressures can result in different amounts of oil being trapped in the cylinder heads, which may not be easily detectable or differentiable.
In one example, the issues described above may be addressed by a method comprising sampling an oil level sensor at targeted time intervals during vehicle motion based at least on lateral and longitudinal vehicle acceleration; and estimating engine oil level based on the sampling. In this way, engine oil level may be sensed dynamically, while a vehicle is moving, allowing for an earlier and more reliable detection of low engine oil levels.
As one example, one or more existing vehicle sensors may be used to assess vehicle dynamic parameters. These include, for example, lateral vehicle acceleration, longitudinal vehicle acceleration, vehicle speed, engine speed, etc. As such, the vehicle dynamic parameters may be parameters that are already being assessed during vehicle operation for other considerations, such as for providing steering assist, or for adjusting suspension settings. Thresholds or ranges may be determined for each parameter and engine oil sampling criteria may be considered met when sampled vehicle data for each of the parameters is within their corresponding threshold or range. The thresholds and ranges may define vehicle moving conditions where engine oil level sensing can be reliably performed, such as during steady state vehicle operation in a substantially straight line. Each time the conditions are met, an oil level sensing may be performed by sending a current to a hot wire oil level sensor.
In this way, by relying of vehicle dynamics data that collected during vehicle operation, engine oil levels can be sampled more frequently. The technical effect of sampling the engine oil level only when selected vehicle dynamics criteria are met is that hot wire oil sensor data can be captured more accurately during vehicle motion. Overall, the robustness and reliability of oil level sensing is improved. By measuring engine oil levels frequently during vehicle operation, an oil leak can be captured earlier in a drive cycle (such as before it can be sensed by a pressure sensor), allowing for earlier addressing of the low oil level. For example, engine oil can be topped off earlier. Alternatively, a potential leak can be identified earlier and service scheduled in accordance.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.